Axial blowers or fans



July 22, 1.958 s. H. Kms-HANSEN AXIAL BLowERs 0R FANS 3 Sheets-Sheet 1 Filed Aug. 27, 1952 I Mi funk s. H. KRISTIANSEN 2,844,303

AXIAL. BLowERs 0R FANS July 22, 1958 3 Sheets-Sheet 2 Filed Aug. 27, 1952 July 22, 1958 S. H. KRISTIANSEN .AXIAL BLOWERS OR FANS 3 Sheets-Sheet 5 Filed Aug. 27. 1952 United States PatentO AXIAL BLOWERS OR FANS Svend Helge Kristiansen, Naestved, Denmark, assignor to Nordisk Ventilator Co., Aktieselskab, a corporation of Denmark Application August 27, 1952, Serial No. 306,669

3 Claims. (Cl. 230-114) This invention relates to improvements in axial blowers or fans provided with wings or blades which are adjustably rotatable on their longitudinal axes.

The object of the adjustable rotation of the blades in such devices is to render possible an alteration of the output of the axial blower. In normal relatively slow operating axial blowers no great diiculty has been experienced in turning the blades during rotation of the blower and thus adjusting the output, It has, however, been found that when axial blowers of the kind concerned are to be driven at a relatively high rotational speed, the blades are subjected to considerable resistances so that a great consumption of force is required to turn the blades. This resistance, which by far surpasses the resistance due to air resistance, is due to the fact that lbesides radial actuation of the blades, the centrifugalA forces acting on each blade produces a torque on the rotation axis of the blade which endeavours to turn the blade to a position in which its main plane coincides with its rotation plane.

An object of the invention is even in rapidly driven axial blowers to make it possible to adjust the blades during rotation of the blower and without for this purpose necessitating a greater power consumption.

Another object of the invention is to provide an axial blower or fan having a rotatable hub ring, at least two blades or wings journalled in said hub ring rotatable on their longitudinal axes and means 'for adjustably rotating said wings or blades, and further having counterweights connected to each of said blades or wings inside the peripheral surface of said hub, said counterweights being so positioned on either side of the main plane of said blade or'wings and so dimensioned that the inertia moments of said wing or blade, including said counterweights, regarding all planes intersecting the axis of rotation of the wing or blade, are approximately equal. In such an axial blower, the counterweights can equalize the torque on the rotation axes of said blades or wings produced by the rotation of the hub ring and due to centrifugal forces.

A further object of the invention is to procure a wing for use in an axial blower having a hub member and at least two blades or wings journalled in said hub members adjustably rotatable on their longitudinal axes, said wing having a wing blade, a root shaft by means of which it is journalled in saidhub member, and at least two counterweights attached to said root shaft in such position that when the wing is placed on said hub ring, said counterweights will be situated inside said hub ring; said counterweights further being so disposed on either side of the main plane of the wing and so dimensioned that the inertia moments of the member comprising the said blade or wing, said root pin and said counterweights, as regards all planes through the rotation axis of the blade, are approximately equal.

Further objects and details of the present invention will be further explained with reference to the drawing, in which 2,844,303 Patented July 22, 1958 Fig. 1 illustrates schematically the forces which act upon the impeller blades of a blower,

Fig. 2 shows a sectional elevation of the upper `half of a blower according to the invention,

Fig. 3 shows a transverse section through a part of a hub ring of the blower shown in Fig. 2, and

Figs. 4 and 5 show two different manners of construction of blades or wings provided with equalizing members according to the invention.

In Fig. l, a disc, indicated by 1, rotates on its axis 2 in the direction indicated by an arrow 3, with a rotational speed of w. In the disc there is rotatably journalled a radially extending shaft 4 carrying a transverse arm 5 (without weight), which at each side of the shaft 4 and at a distance r from shaft 4 carries a mass m. These two masses represent two points of a rotatable blade. The arm 5 forms an angle a to the rotation plane of disc 1 perpendicular to axis 2 and indicated by a line X. In this position the distance of each mass m1 to line X is equal to b, and its distance from a plane through shaft 4 perpendicular to the rotation plane as indicated by line y, is equal to a. In the position shown the distance of each mass m from the axis of rotation 2 is indicated by A.

During rotation of disc 1 each mass m` will be actuated upon by a centrifugal force K/ C=a1/A From this is obtained M =a.m.Aw2.b/A=mw2.a.b (I) From the diagram it is, however, likewise evident that a=r cos a, and b=r sin a which gives M=m.w2.r2. sin a; cos a=1/2 m.r2.w2. sin 2 The value m. a. b. expressed in Formula I indicates the centrifugal moment of the mass m as regards lines X and Y. It is further more apparent from Fig. 1 that masses in the l and 3 quadrant of the co-ordinate sys-- tem formed by lines X and Y will, owing to the effect of the centrifugal forces, produce uniformily directed moments of rotation, while masses in 2' and 4 quadrants will produce moments of rotation which are oppositely directed to the moments of rotation produced by the masses in l and 3 quadrants. Thus, the above stated expression for M, when a and b are calculated with signs, likewise indicates the direction of the moment of rotation.

Furthermore it is apparent that the moment of rotation acting upon the system shown may be obviated if there is added a new system, the centrifugal moment of which on lines X and Y is numerically equal to the -centrifugal moment of the systems shown, but having unlike signs.

This may also be expressed by the combined system, i. e. the mass system shown and the mass system added, having a centrifugal moment of zero in relation to lines X and Y, if the moments of rotation on the combined mass system are to be equalized.

When furthermore, as the case is according to the invention, it is desired that the moment of rotation produced by the action of the centrifugal forces on the cornbined system shall be zero, or approximately zero, at all angular position ofthe system on shaft 4, it must be demanded that the kcentrifugal moment of the con bined system on any ,relatively perpendicular axes in the X-Y plane shall be equal to, or approximately equal to zero. l

lf that which is explained above in connection with single masses in a plane is extended to comprise bodies, it will be noted that the moment of rotation due to centrifugal forces and `acting on .the rotation axis 4 of the body may be equalized by providing the body with counterweights in such a manner that the centrifugal moments of the member comprising the body and the counterweights, as regards any two relatively perpendicular planes through the rotation axis, will be zero.

When,.however, the centrifugal moments of a body as regards any relatively perpendicular planes through an axis is zero, the inertia moments of the body as regards any plane through the said axis will be equal, and conversely. By the determination of the size and position of the counterweights it is thus possible to consider the said inertia moments which are much easier to compute than the centrifugal moments.

When the inertia moments of a body as regards two relatively planes through an axis are of equal value, and the centrifugal moment as regards the same two planes at the same time are zero, the inertia moments as regards any other planes through the rotation axis will also be of equal value.

The result -of this will be that when determining the size and position of the counterweights, there is rst found for the -unbalanced body vthe relatively perpendicular planes through the rotation axis which produce respectively maximum and minimum inertia moment. As regards these planes the centrifugal moment will at the same time be zero. After this it is a simple matter to calculate the size and positioning of the counterweight.

An axial blower in which the impeller blades are balanced as stated above, is shown in Fig. 2. In this iigure indicates a shaft rotatably journalled in roller bearings 22 within a housing 24. On the shouldered front end of shaft 20 an angular ring 26 is secured by means of a key 30 and a nut 28 screwed on a threaded part of shaft 20. By means of the said nut 28 the ring 26 is pressed against shoulder 32 on shaft 20.

A hub 34 is welded or soldered to ring 26. This hub is provided with flange 36 supporting a hub ring 38 having a number of bearing channels 40, see Fig, 3, within each of which a .root shaft 44 of an impeller blade 46 is journalled by means of ball hearings 42.

Between the walls 48 of channels 40 hollow spaces 50 are formed within the hub ring 38 for reducing the weight of the said ring.

Each blade 46 *has a root plate 52 disposed within a recess 54 in the peripherical surface of hub ring 38.

The root shaft `44 projects outside the inner surface of the hub ring 38 where it carries a supporting member 56 secured to the threaded shaft end by means of a nut 58 and a key and tongue connection (not shown). By means of this nut 58 the supporting member 56 is pressed against the lower ball cage 60 of the innermost bearing 42.

The supporting member 56 has three arms 62, 64 and 66. The one arm 62 is placed in the centre plane of the blade 46and has at its free end a ange 68, Fig. 3, in which a pin 70 is secured. Beneath the ange 68 a roller 72 is rotatably journalled on the pin 70 by means of a ball bearing 74.

Roller 72 engages a groove 76 formed between two rings 78 which by means of bolts 80 are secured to a conical disc 82. The disc 82 is provided with a number of enlargements 84 each having an axially extending bore for a pin 86, the disc 82 being slidable on these pins 88. The pins 88 are secured to the hub 34 by means of nuts 90, and thus the disc 82 will partake in the rotation of the hub. Further this disc 82 is journalled on a shaft 94 by means of a ball bearing 92. The shaft is slidably and rotatably journalled and guided in a central bore 96 in the reduced end of shaft 20. By means of a pin 99 the one end of a connecting link 100 is pivotally connected to the free end of shaft 94. The other end of said connecting link is by means of a pin 102 pivotally connected to the downwardly extending arm of a doublearmed lever 104 fulcrumed on a pivot pin 106 attached to a bracket 108 secured to a cover 110 which by means of bolts 112 is secured to a partition 114 in a housing 116 disposed at the front end of the blower.

The upwardly extending arm of lever 104 is provided with a handle 118 by means of which the lever may be pivoted for adjustable longitudinal displacement of the shaft 94. A springloaded pin 120 on the upper arm of lever 104 is arranged to engage any one of a number of notches 122 in a plate 124 xed to the bracket 108 for holding the lever, and consequentlythe shaft 94, in an adjusted position.

Upon longitudinal displacement of the shaft 94 the conical disc S2 is also displaced, thereby turning the impeller blades 46 in consequence of the engagement of roller 78 with the groove 76 on disc 82.

To the free end of each arm 64 and 66 projecting from the supporting member 56 is attached a counter weight 126. Each of these counter -weights 126 is so disposed and has a such mass that for the purpose set forth above, the inertia moments of the member comprising blade 46, root plate 52, root shaft 44, and supporting member 56 with arms 62, 64 and 66, roller 78 and counter weights 126, as regards all planes through the rotation axis of the blade 46 are approximately equal.

In the arrangement shown in Figs. 2 and 3 the counter vweights are positioned relatively close to the rotation axis of the blower. It is to be noted that the radial distance of the Weights from the rotation axis of the blower as evident from the above stated formula for M, has no inuence on their equalizing effect, for vwhich reason it is preferred that they are positioned as closely as possible to the rotation axis in Vorder to reduce as much as possible the centrifugal forces due to the counter weights.

A modified manner of arranging the counter weights on impeller blades or similar wings is known in Fig. 4. In this instance the impeller blade 46 with root plate 52 and root shaft 44 is rotatably journalled in the hub ring 38 in the same manner as shown in Figs. 2 and 3 but only shown schematically in Fig. 4. The root plate 52 has two grooves 128'in each of which a counter weight 130, preferably made of lead, is secured. By this arrangement the counter-weights take up only very little space, but they are positioned a somewhat .greater distance from the rotation axis of the blower'than in the arrangement shown in Figs. 2 and 3.

It is to be noted that the weights need only be so dimensioned and positioned that they approximately equalize the forces of the moment of rotation mentioned above, since besides these forces other resistances opposing the rotation of the blades may arise, e. g. air resistance, which it is not possible to equalize. For this reason it is only required to equalize forces of the moment of rotation to such yan extent that the value of these forces do not essentially exceed other forces opposing the rotation of the blades. The result of this is that in calculating and positioning the weights the necessary practical considerations may be taken.

From the Formula II given above for M it will further be noted that the said moment is only dependent on m2 and u, since for a given member the value m.r2 is constant. The forces of the moment of rotation mentioned may therefore be equalized by means of other forms for counter Weightsthan have an effect which is dependent on a and o2. Thus it is possible to employ a counter weight arrangement as the modification shown in Fig. 5.

In this construction the impeller blade 46 with root plate 52 and root shaft 44 is journalled in the hub ring 38 in the same manner as `shown in Figs. 2 and 3 but only shown schematically in Fig. 6. The lower end of the root shaft 44 carries a bevel gear 132 meshing with another bevel gear 134 half the size of the gear 132. The smaller bevel gear 134 is attached to a shaft 136 journalled in bearings 138 and 140 on the hub ring 38 and carrying a counter weight 142. When the blade 46 is rotated in the manner shown in and described in connection with Figs. 2 and 3, the counter weight 142 will swing outwards an angle which is double the size of the angle at which the blade 46 is turned. This counter Weight 142 will be aifected by the centrifugal force which is directly proportional to wz, and will produce an eiect upon the blade 46 which is dependent on as well angle or more correctly angles 2a and m2, and will thus be able to produce an eifect which obviates the effect of the moment of rotation in question.

I claim:

l'. In an axial fan, for use in connection with a driving shaft, in combination, a hollow hub member mounted on said driving shaft, said hub including la hub ring, at least two wings journalled in said hub ring rotatably about their longitudinal axes, eachwing comprising a wing blade and a root shaft, said hub ring having a through bore forv each of said root shafts, each root shaft mounting inside said hub ring a laterally extending adjusting arm, an inwardly extending actuating pin connected to said adjusting arm, an adjusting shaft mounted for reciprocation coaxially with said hub, an adjusting disk member rotat.- ably mounted on said adjusting shaft, means operable for restraining axial displacement of said adjusting disk relative to said adjusting shaft, at least one driving stud interconnecting said hub member land said adjusting disk member for securing the same rotational speed of said two members, said adjusting disk having a peripheral groove opposite each of said ractuating pins, each actuating pin engaging said groove, means operable for axially displacing said adjusting shaft thereby to |adjust the axial position of said disk and by way of said actuating pin and said adjusting arm to adjust the pitch of each wing, `at least two counterweights secured to the root shaft of each wing and disposed inside the peripheral surface of said hub ring, said two -counterweights being positioned on either side of the main plane of each wing, and the inertia momentum of each wing with all members secured thereto including the said root shaft and said counterweights being approximately equal with respect to all planes coincident with the -axis of rotation of the wing.

2. An axial fan, as claimed in claim 1, said hub ring having for each wing a recess formed in the peripheral surface of the hub ring concentric with the said bore, each wing including a root plate between said wing blade and said root shaft, said root plate being disposed within said recess and having at least two grooves at either side of the main plane of the wing, said two counterweights being secured to said root plate and each disposed within one of said twov grooves. l

3. An axial fan, as claimed in claim 1, at least tw inwardly inclined supporting arms having free ends and being secured to said root shaft inside said hub ring disposed on either side of the main plane of each wing, each counterweight being secured to one of said two supporting arms.

References Cited in the file of this patent UNITED STATES PATENTS 1,404,403 Parker Jan. 24, 1922 1,482,690 Lanzius Feb. 5, 1924 1,761,690 Steinmetz June 3, 1930 1,967,461 Ballew July 24, 1934 1,980,272 Havill et a1 Nov. 13, 1934 2,030,953 Gemeny Feb. 18, 1936 2,054,947 Riddle Sept. 22, 1936 2,146,334 De Caria Feb. 7, 1939 2,219,303 Fraser Oct. 29, 1940 2,225,209 Dewey Dec. 17, 1940 2,316,940 Dewey et al Apr. 20, 1943 l 2,353,334 Haugh July 11, 1944 2,407,630 Dewan Sept. 17, 1946 2,479,668 Brandon et al Aug. 23, 1949 2,552,727 Lightfoot May 15, 1951 

